The invention relates to a system for monitoring the front or rear parking space of a motor vehicle and, more particularly, to a system having a video camera built into either the front or rear of the vehicle and a viewing and monitoring device in the field of view of the vehicle driver connected to the camera. The field of view is fitted with a display screen.
Approach problems during the parking of vehicles, such as avoiding other vehicles, walls and the like, are well known. Known active systems which attempt to alleviate the approach problems, such as those having infrared light and/or ultrasonic sensors, suffer from a lack of measurement accuracy, reliability and reproducibility.
One alternative is represented by rear space video cameras, whose use in the area of commercial vehicles, such as airport courtesy vehicles, is already known. While the use of such video cameras, specifically in private cars, would be desirable due to the fact that parking spaces are becoming ever tighter, often requiring driving accuracy to within centimeters, the increasingly obscure rear parts of vehicles make this more difficult. The rear geometry of normal private cars, however, makes extremely wide angle lenses necessary. Unfortunately, such wide angle lenses provide the vehicle driver with an image which can hardly be interpreted.
There is therefore needed a system for monitoring the front or rear parking space of a motor vehicle which delivers to the vehicle driver a clear and easily interpretable display of the vehicle front or rear space and its boundary edges or obstacles.
These needs are met according the present invention by a system having a video camera built into either the front or rear of the vehicle and a viewing and monitoring device in the field of view of the vehicle driver connected to the camera. The field of view is fitted with a display screen. The video camera is equipped with means for its pivoting (turn and tilt) as a function of electric drive signals and is of the type having object referenced image sharpness control of its optics. This sharpness control is effective over the whole image angle detected, so that a corresponding sharpness measuring field is capable of following an object once detected over the whole screen. The system further includes an image processing unit which subdivides the image picked up into fields or quadrants and/or an edge region outside and a central region inside an auxiliary frame. The image processing unit is capable of discerning the instantaneous position of the sharpness measuring field with reference to at least one of the fields or quadrants and/or to the auxiliary frame and, as a function of a tendency of the sharpness measuring field to leave the original field/quadrant, not to reach a predetermined field or predetermined quadrant and/or to cross from the central region over the auxiliary frame out into the edge region of the image field. The image processing unit generates the above-mentioned drive signals for the pivoting means according to the measure that the pivoting of the camera thereby effected counteracts the triggering tendency or neutralizes or eliminates the triggering tendency.
The present invention makes use of the fact that modern video cameras, which increasingly are controlled by "fuzzy logic", can follow an object once detected, in terms of its sharpness, with the autofocus (AF) over the whole search field or over the whole image angle, by which means the distance measuring field or sharpness measuring field moves along with the object, that is to say, in the case of its approach or removal is virtually dragged with it. In this respect, the sharpness adjustment is no longer search-field-referenced but object referenced.
According to the present invention, this property is used for an electronic tracking of the viewing angle of such a video camera used for rear-space or front-space monitoring. Because of this, an object limiting the rearward or forward penetration depth of the vehicle can be seen up until contact, for example, with the bumper and the remaining distance up until its disappearance can be seen or easily judged.
In this case, as a whole, the device according to the invention exhibits the advantage that camera lenses of very compact construction can be used, without the requirement of extending the camera for the purposes of realizing a sufficient viewing angle. The assembly of the camera is thus possible within the vehicle contour. The image interpretation is simplified for the driver by the concentration of the image section on the essential obstacle, and complicated image processing and image preparation, as are unavoidable in the case of extreme wide angle optics, can be eliminated.
Accordingly, a "passive" system having an object-referenced guided video camera can be supported at least by means of an additional "active" system, for example an ultrasonic or infrared or laser system. Such an additional system either acts redundantly in situations in which the passive system is subject to functional limitations. Alternatively, signals from at least one such additional system support the active detection of obstacles on the camera side, for example in the case of rear space monitoring.
The use of an additional active system proves advantageous, for example in the case of obstacles having a low structure, in which autofocus control of a video camera via fuzzy logic can also fail or, on its own, delivers too large a decision time delay.
Differing from conventional active ultrasonic or light measuring systems, at least one additional system of this type can therefore be primarily used here not for warning or giving alarms, but for influencing or supporting the capture and object following behavior of the electronic autofocus function of a video camera. By means of connecting the passive system to at least one of the above-mentioned active systems in a device, the respective weaknesses of the relevant individual systems are thus overcome in any case.
As a whole, the present invention clears essential obstacles which previously stood in the way of the use of video cameras, especially in the rear space monitoring of private cars. It is self-evident, that the possibilities of use of the device according to the invention are not limited to the rear space of a vehicle; a corresponding device can nonetheless also be provided and used for monitoring the front space of a vehicle.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.